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The article is about declining central air conditioner efficiency as it ages.  Al’s Plumbing, Heating & A/C in Plano, Texas provides maintenance & repairs for all brands of Central A/C, Gas & Electric Furnace, and Heat Pumps.    Additionally we sell and install new HVAC Systems from American Standard (same company as Trane), Ameristar (same company as American Standard) and Coleman HVAC (same company as York HVAC).

Al’s also provides full service plumbing maintenance, repairs and replacements for every plumbing component in your home.  Al’s sells and installs Rheem Professional Series gas & electric water heaters, and tankless water heaters.  Al’s is near your home in Plano, TX; Allen, TX; and Frisco, TX.  We service all homes in southern Collin and Denton Counties with no additional travel charge.

Call Al’s today to discuss any concerns or problems you have with your HVAC System or Plumbing.  We will arrange an appointment at your convenience and offer 24/7 Emergency Service.

 

Image Source: Dreamstime.com

Does Central Air Conditioner Efficiency Decline With Age?

There are many opinions about declining air conditioner efficiency with age.   We found a 2018 Long-Term Scientific Study that details declining air conditioner efficiency with age — and by how much.  The Research Study reported findings on declining efficiency of residential Central A/C and heat pumps over a period of 2–5 years.   The findings were based on about 56 residential air conditioners and heat pump in Florida homes — with over 1,500 hours of A/C use per year. 

 

Click Here To Read The Full Research Report:  Scientific Study Report On Declining Air Conditioner Efficiency With Age

 

There Are Many Ways To Decrease Cooling & Heating Costs Without Replacing Your HVAC System.   

Click Here For Our Articles Detailing These Savings’ Opportunities: 

  • 25 Uncommon Ways To Lower Heating & Cooling Costs: https://www.alsplumbing.com/lower-heating-costs-20-uncommon-ways-part-1-of-3/

The Primary Causes Of Declining Air Conditioner Efficiency With Age:

Click Here To See A Diagram Of A Central Air Conditioner & Furnace: HVAC System Diagram

  • First we will discuss the biggest reasons for declining air conditioner efficiency with age
  • At the end of this article we present our summary of the Research Study’s findings on declining air conditioner efficiency as the unit ages. 

 

Leaking Ductwork — Decreased cooling efficiency / ability up to -10% to -25%.

Most homes lose 10-25% of the cooled / heated air through leaks in ductwork. *4

Click Here To See Leaking Ductwork:  Leaking Attic Ductwork

Click Here To See Damaged Ductwork: Damaged (torn) Attic Ductwork

Click Here To See Damaged Ductwork: Attic Ductwork With Holes

Click Here To See Damaged Ductwork: Damaged (collasped) Attic Ductwork

 

*4 Source: https://aeroseal.com/air-duct-sealing-blog/duct-leakage-101-what-is-duct-leakage/

 

Dirty Furnace Filter — Decreased efficiency up to -15%.

dirty air filter on left. New air filter on right.

Image Source: Can Stock Photo

Shown: A very dirty furnace filter on left.  A new or clean filter on the right.

 

The United States Department Of Energy (DOE) States: “Replacing a dirty or clogged filter will lower your air conditioner’s energy use by up to 15%. **

** Source: https://www.energy.gov/energysaver/maintaining-your-air-conditioner

 

Dirty Indoor Cooling Coil (evaporator coil) — Decreased efficiency up to -19%.   

NOTE:  The indoor cooling-coil (evaporator coil) is inside the furnace or ductwork and can’t be seen without removing a panel.

The home’s indoor air passes through the indoor cooling-coil (evaporator coil) while the A/C is running.    When your home’s indoor air passes through the indoor cooling-coil — it removes the heat and the humidity as the air passes through.  You must have clean coils for your air conditioner to perform at maximum efficiency.  If the coil is clogged the A/C to run longer & harder.

A clogged indoor cooling coil reduces the amount of air-flow through the coil  — causing the efficiency of the A/C to notably drop.  One study says that if the indoor cooling coil is 1/3 clogged — it reduces A/C’s cooling ability by as much as -19%.  So, it’s fair to say 1/3 clogged indoor cooling coil increases cooling cost by +19%.  It also causes the HVAC system to run 19% longer and harder — and wear out at least 19% faster.  *5

 

The indoor cooling coil is wet when the A/C is running because this coil removes humidity from the home’s indoor air.  Because it’s wet, the coil catches dust (that passes through the furnace filter) quite easily.

Dust & water create a perfect environment for mold growth.  When the indoor cooling (evaporator) coil is molded — each time the furnace blower fan is running it’s blowing mold-spores all over your home.  The photo we provided shows the dust clogging the indoor cooling coil to be black with mold.,

 

Click Here To See A Diagram Showing The Location Of The Indoor Cooling (evaporator) A/C Coil:  Location Of Indoor Cooling (evaporator) Coil

Click Here To See A Clogged & Molded Indoor Cooling (evaporator) A/C Coil: Dirty & Molded Indoor Cooling (evaporator) Coil

Click Here To See A Completely Frozen Indoor Cooling Coil: Frozen Indoor A/C Cooling Coil

Note: Frozen Indoor Cooling Coil Is Due To: 1. Not enough air flowing through it (typically because of a dirty air filter).  -OR- 2. Low refrigerant charge.

 

*5 Source: https://www.airah.org.au/Content_Files/TechnicalPublications/hvac-factsheet-cleaning-coils-09-13.pdf

 

 

central air conditioner outside unit

Image Source: DreamsTime.com

Dirty Outdoor A/C Outside Unit (condenser) Coil — — Decreased efficiency by up to -30%. 

 

Click Here To See The Before & After Cleaning Photos Of A Completely Clogged Outdoor A/C Unit Coil: Before & After Cleaning Photos Of Clogged Outdoor A/C Unit Coil

 

The United States Department Of Energy States: “A dirty condenser coil can increase outdoor unit energy consumption by up to 30%.”  ***

 

*** Source: https://www.buildings.com/article-details/articleid/8282/title/clean-hvac-system-coils-save-energy

 

Dirty Furnace Blower-Fan

Dirty Furnace Blower-Fan Motor

Click Here To See How Dirty A Furnace Blower & Blower Motor Can Get: Very Dirty Furnace Blower & Blower Motor

NOTE: Furnace filters don’t remove all the airborne dust that flows through them.  If filters were that efficient — very little air could pass through the filter.   Over time, even with the best furnace filter maintenance, dust will build up on the blower fan and the blower motor.  A dirty blower fan cannot move as much as as it’s supposed to, and is designed to.   A dirty blower motor will overheat.  This will affect its performance and cause it to wear out faster.

air conditioner refrigerant and gauges

Shown: Air Conditioner Refrigerant-Tank & Installation Gauges

Image Source: Shutterstock

  • Low Refrigerant Level

A 1978 study of 511 failed air conditioners determined that 17% failed due to low refrigerant.     Source: The study described within this article — a link to the study is at the top of this article.

To cool at maximum efficiency, an air conditioner (or heat pump) must be fully charged with refrigerant.  Low refrigerant causes the A/C to run longer & harder — reducing its lifespan and increasing cooling bills.   During peak summer heat, an A/C that’s low on refrigerant won’t be able to keep the house cool.

The refrigerant must stay at a specific charge / level.  If the refrigerant level drops, it reduces the air conditioner’s cooling power.  Refrigerant does not get used up.  If refrigerant is low — it’s due to a leak, corrosion, or loose connections somewhere along the refrigerant line.

The report stated: “A system 20% low of refrigerant (in a 3-ton / 36,000 BTU system)  — typically leads to a -24% decrease in cooling capacity at a 95°F.  The actual decrease in A/C efficiency is directly related to how low the refrigerant level is.  For this reason there is no average decrease in efficiency due to low refrigerant

Low refrigerant reduces the indoor cooling coil’s ability to remove heat from indoor air.   Once refrigerant level drops enough, the indoor cooling coil will begin to freeze because the refrigerant’s temperature can’t rise high enough inside the coil.  Then the coil develops ice and eventually the coil will freeze completely.

Low refrigerant also lowers efficiency of the outdoor A/C unit.    The compressor in the outdoor unit is designed to operate with a specific amount of refrigerant.  If refrigerant gets low enough, the outdoor unit’s compressor will work longer and harder — shortening it’s lifespan.

 

Let’s Do The Math — If You Have All These:

leaking ductwork (10-25%)

dirty furnace air filter (up to 15%)

dirty indoor cooling coil (at least 15%)

dirty outdoor unit coil (up to 30%)

Your cooling bill is as much as +85% higher than if these items were properly maintained!   

 

If you also have low refrigerant level — your cooling bill could be double or higher.

 

These same percentages apply to how much faster the A/C is wearing out.   If it has to run twice as long — the HVAC System wears out twice as fast. 

 

All of These Problems Will Be Identified With A Spring A/C Tune Up.   

 

Our Summary Of The Scientific Report For Declining Air Conditioner Efficiency With Age

Using an analytical approach, air conditioning performance falls between 3.7% per year, on average.  This suggests that mechanical cooling system performance degrades over time in a measurable fashion if tracked by weather-related influences.

  • Decreasing Air Conditioner Efficiency Is Primarily Attributed To: System Age, Seasonal Energy Efficiency Ratio (SEER), and System Size.
  • System size/capacity appearing to be the largest factor for declining efficiency.
  • Larger systems appeared have higher levels of decreasing efficiency — and they have shorter life expectancy.
  • For each additional 1 ton (12,000 BTU) — cooling efficiency decreased an additional up to +3% per year.
  • It’s speculated this may be due to larger systems operateing at much higher air-flow rates.   This contributes to higher levels of air-filter clogging and indoor cooling-coil fouling.
  • Another contributing factor is if the existing ductwork & registers are undersized for the size of the A/C
  • The cooler the home is kept, the more the A/C must run — and the faster the system wears out.
  • This is also the case in homes with insufficient insulation.
  • Higher SEER equipment appeared more resistant to decreasing efficiency.
  • A 3-ton system with a SEER of 20 declined in efficiency by -1% less per year.
  • The study determined an average annual decrease in cooling efficiency of 5.2% per year in the Florida homes studied.
  • The Dept. Of Energy (DOE) stated 3% per year — but this number likely represents homes all over the U.S.
  • An air conditioner in Minneapolis runs a lot less than one in Florida.  The less it runs, the less cooling-efficiency will decrease per year.
  • With an average decline of -5.2% — system declines ranged from -8% to -40% per year.
  • The study found the amount of annual cooling-efficiency decline became higher as the system aged.
  • Sudden & severe declines in performance typically indicated the need for system replacement.

 

How Much Declining Cooling-Efficiency Increases Cooling Costs

  • At 10 cents per kWh — the annual cooling cost increase is +$21.50 per year for each year of age — for a 3-ton / 36,000 BTU central A/C.
  • In year 5 — the total additional electricity cost (due to declining efficiency) = +$108.00 ($21.50 x 5 = $108.00) — for a 3-ton / 36,000 BTU central A/C.
  • The cooler the home is kept, the more the A/C must run — and the faster the system wears out.
  • This is also the case in homes with insufficient attic insulation.

 

Texas Homes Insulation Levels That Were Common — Or Became Required By Building-Code

           Attic Insulation                           Wall Insulation

  • 1950’s: none                                     none
  • 1965-1970: R-13 (3.5″ BATT)      Wall Insulation: R-6 (2″ BATT)
  • 1970’s:  R-19 (6″ BATT)                 Wall R-6  (2″ BATT)     *3
  • 1980’s: R-30 (9″ Blown)                Wall R-13 (3.5″ BATT) *4
  • 2014:    R-38 (15″ Blown)               Wall R-15                         *5
  • *3 Source: https://snuggpro.com/blog/item/many-homes-built-prior-to-1980-were-built-without-insulation-in-the-walls
  • *4 Source: https://www.jlconline.com/how-to/insulation-code-change_o
  • *5 As required by the 2012 Edition of the International Building Code (IBC)

 

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The article was about declining central air conditioner efficiency as it ages.  Al’s Plumbing, Heating & A/C in Plano, Texas provides maintenance & repairs for all brands of Central A/C, Gas & Electric Furnace, and Heat Pumps.  Additionally we sell and install new HVAC Systems from American Standard (same company as Trane), Ameristar (same company as American Standard) and Coleman HVAC (same company as York HVAC).

Al’s also provides full service plumbing maintenance, repairs and replacements for every plumbing component in your home.  Al’s sells and installs Rheem Professional Series gas & electric water heaters, and tankless water heaters.  Al’s is near your home in Richardson, TX; Garland, TX; and northeast Dallas, TX.  We service all homes in southern Collin and Denton Counties with no additional travel charge.

Call Al’s today to discuss any concerns or problems you have with your HVAC System or Plumbing.  We will arrange an appointment at your convenience and offer 24/7 Emergency Service.